1. Field of the Invention
The present invention relates to a technique for performing current control in accordance with the maximum rated current of an kind of AC adapter applied to, e. g., a personal computer.
2. Description of the Related Art
In recent years, various types of personal computers such as desktop personal computers and notebook personal computers have been manufactured and sold. In general, a series of models having different CPUs or different optional devices are prepared with respect to each type of personal computer. Furthermore, recently, a so-called BIO (built-in order) service has been gradually diffused. In this service, the system of a computer is configured in accordance with a customer's request.
Moreover, such a type of personal computer as stated above is made to allow an AC adapter for AC power supply to be connected to the personal computer. Usually, when the personal computer is used indoors, one end of the AC adapter is connected to the personal computer, and the other end is connected to a wall outlet. Each of the AC adapters is defined the maximum rated currents. Thus, the power consumption of the personal computer is controlled by a power controlling device in accordance with the maximum rated current of an AC adapter (see, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2002-222031).
As is often the case, all of a series of models of personal computers incorporate the same type of power controlling devices as their parts. Thus, until now, the same kind of AC adapters have been packed along with all of the series of personal computers. As the kind of AC adapter, an AC adapter adapted for one of the models of personal computers, which incorporates a CPU having the highest performance and thus has the largest power consumption, has been adopted. Also, each of the power controlling devices has been set to perform current control in accordance with the maximum rated current of the above adopted AC adapter.
However, when an AC adapter adapted to a model of personal computer incorporating a CPU having a high performance is packed along with a model of personal computer incorporating a CPU having a low performance, the total cost of the AC adapter and the personal computer is inevitably high. This is disadvantageous for both the manufacturer/distributor and the customer. On the other hand, it is not realistic that in order that suitable AC adapters be respectively applied to a number of models of personal computers with respect to the maximum rated current, different power controlling devices designed to perform respective current controls in accordance with the maximum rated currents of the AC adapters are provided in the models of personal computers, respectively. This will also increase the above total cost. It is therefore preferable that the same type of power controlling devices applicable to a number of kinds of AC adapters be provided in the series of personal computers, and be made to perform current controls in accordance with the maximum rated currents of the AC adapters applied to the personal computers, respectively.
And now, in the case where the same type of power controlling devices applicable to a number of kinds of AC adapters are adopted in respective personal computers, it is necessary to recognize the kind of an AC adapter packed along with a personal computer. As a method of recognizing the kind of the AC adapter, for example, there can be a method using a specific switch, or a method of providing an identification signal line to a connector for an AC adapter, and detect the state of the identification signal line, with a voltage applied, at the time of connecting the AC adapter to the personal computer. However, provision of such a mechanism for recognizing the kind of an AC adapter will also cause the cost to be increased, and also the space required for the computer and the mechanism to be increased.